New Sim card for new byop

[pGolay]

Hello - My current BYOP is being replaced but the new one takes a different sized SIM than the old phone. I bought a new Sim kit, but

1. I am not certain which SIM (ATT, Verizon, T-Mobile) works in my area.
2. I need help getting my current account to point at my new SIM.

Old= Moto G3 ; New = Moto G Power

cheers.

[LindaCHU]

Use the same network SIM that is currently in your phone.
Do you not know what service you have?